Non-destructive Depth Dependent Stress Monitor

Aircraft landing gear, and wheels in particular, are subjected to heavy loads during service. Controlled surface compressive stresses help to improve the fatigue life by reducing the probability of crack initiation and propagation from the wheel surface. Manufacturers such as Allied Signal will induce a surface compressive stress by either shot peening or roll burnishing. Acoustic and magnetic methods for determining stress by either shot peening or roll burnishing. Acoustic and magnetic methods for determining stress are difficult due to numerous microstructure parameters which alter the propagating wave. X-ray diffraction provides a direct measure of the residual strain independent of other microstructure properties, but is typically limited to the first 30 um of depth. Traditional four circle scanning diffractometers for stress analysis are very slow, and ill suited for manufacturing environments. ATMI in collaboration with Proto Manufacturing, and Allied Signal Aircraft Landing Systems, proposes to develop a rapid x-ray stress technique capable of rapid depth dependent stress monitoring. The technique will utilize a novel dual (short and long) wavelength z-radiation source applied to an existing commercial high speed fiber-optic/x-ray stress analyzer manufactured by Proto. In Phase II a beta site system will be tested Allied Signal's manufacturing facility.